An arrangement of this kind is known from WO 2004/018039 A1, which particularly describes a system and method for the local heating of a target region of an object by varying the magnetization of magnetic or magnetizable substances. A magnetic field is generated whose magnetic field strength varies in space in such a manner that a first sub-region of low magnetic field strength and a second sub-region which encloses the first sub-region and has a higher magnetic field strength are formed in the target region (also called region of action). Subsequently, the position in space of the two sub-regions in the target region is varied with a given frequency for so long that the particles are heated to a desired temperature due to frequent variation of the magnetization.
A so-called Magnetic Particle Imaging (MPI) arrangement and method is known from Gleich, B. and Weizenecker, J. (2005), “Tomographic imaging using the nonlinear response of magnetic particles” in Nature, vol. 435, pp. 1214-1217. The arrangement and method for magnetic particle imaging (MPI) described in that publication takes advantage of the non-linear magnetization curve of small magnetic particles. Signals are recorded which are dependent on the magnetization in the examination zone, which magnetization has been influenced by the shift in the position in space of the sub-zones, and information concerning the spatial distribution of the magnetic particles in the examination zone is extracted from these signals, so that an image of the examination zone can be formed. Such an arrangement has the advantage that it can be used to examine arbitrary examination objects—e.g. human bodies—in a non-destructive manner and without causing any damage and with a high spatial resolution, both close to the surface and remote from the surface of the examination object.
A number of materials are available that give a good signal in MPI, such as Resovist®. For a magnetic particle to react to an ac magnetic field, different mechanisms may be responsible: (1) Néel rotation in the case of single-domain particles, (2) geometric Brownian rotation, and (3) domain wall movement for multi-domain particles. For MPI, magnetic particles are optimised for the Néel rotation, which allows for a fast response to the external field so that the non-linear magnetization response can be analyzed in a good number of harmonics.
Magnetic hyperthermia stands for a local heating effect that can lead to apoptosis of tumor cells (thermoablation) if the local temperature exceeds the window 42-45° C. In combination with other cancer treatment modalities such as brachytherapy, local moderate heating may result in an increase in efficacy of the combined method. Local heating can be realised due to the presence of magnetic nanoparticles in tumor cells or in close vicinity thereof. Magnetic nanoparticles are usually administered intratumorally.